Well, after diggin on the mysql website for the plesk error above ( http://dev.mysql.com/doc/refman/5.0/en/mysql-upgrade.html ) , I issued these commands from telnet and it fixed the plesk admin center which started normal:
# mysqlcheck –check-upgrade –all-databases –auto-repair –user=admin –password=youradminpassword
then issue this command:
# mysql_fix_privilege_tables
I got error because of the mysql connection needs the admin user username and password since this is the database user used by plesk, so I issued this command manually:
# cat /usr/share/mysql/mysql_fix_privilege_tables.sql | /usr/bin/mysql –no-defaults –force –user=admin –password=youradminpassword –host=localhost –database=mysql
Now Plesk is working normal, mysql is working normal, php 5.2.6 is working normal, so everything updated and working.
Will update here if any issue …